Ball-bump bonded ribbon-wire interconnects are desirable for enabling a ribbon-wire to be bonded to an integrated circuit's bond pad that is narrower than the ribbon-wire. Ribbon-wire is used when a wide signal path is desirable to limit signal loss of a high-frequency signal or avoid other adverse performance effects. Thermo-sonic wire bonding equipment exists that can place ribbon-wire interconnects, but existing techniques are limited because they require bond pads that are of equal or larger size than the ribbon-wire's width. The ribbon-wire is captured between the bond tool's foot and the pad in order to apply ultrasonic energy and force to form the bond between the ribbon-wire and the bond pad's metallization. The resulting bond establishes an electrical connection between the ribbon-wire and the bond pad's metallization.
Therefore, the bond tool must be able to touch down on each land to form the bond, and the contact area for each bond pad must be of the same size or larger than the bond tool to properly form a bond. The problem with using the wide ribbon-wire on a narrower bond pad is that the contact areas are not the same. With a given amount of energy delivered to a smaller area when there is a smaller bond pad, adverse results can occur, including failure of the bond due to excessive energy concentration. Therefore, the combination of ultrasonic energy, force, and time must be controlled to limit the energy transferred into the bond in this circumstance.
Furthermore, the bond pads are typically on the same surface as the integrated circuit itself or can even be recessed, which prevents the bond tool from reaching a pad without first making potentially damaging contact with the surface of the integrated circuit. Additionally, the ribbon-wire is opaque, which makes it impossible to visually locate the bond pad through the ribbon-wire to determine when the bonding tool is properly positioned to create a bond.
The use of wire-mesh interconnects is known in the prior art. Wire mesh is used in the form of a ribbon or strip. However, hand cut pieces of gold wire-mesh are needed and have been placed manually to connect the gold wire-mesh to a bond pad having a width that is less than that of the wire-mesh. Wire-mesh enables the bond location to be viewed through the wire-mesh, which facilitates the manual alignment to a bond pad in a manner that is not possible with opaque ribbon-wire. However, this existing method requires extensive manual effort to create multiple bonds on intersections of the wire-mesh for each interconnect placed. Furthermore, when wire-mesh is bonded to a narrower bond pad, the overhanging mesh in some cases must be folded up to avoid short circuits, requiring additional manual effort.
Therefore, a need exists for a new and improved ball-bump bonded ribbon-wire interconnect that can be used for enabling a ribbon-wire to be bonded to an integrated circuit's bond pad that is narrower than the ribbon-wire. In this regard, the various embodiments of the present invention substantially fulfill at least some of these needs. In this respect, the ball-bump bonded ribbon-wire interconnect according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of enabling a ribbon-wire to be bonded to an integrated circuit's bond pad that is narrower than the ribbon-wire.